The Analytical Instrumentation Core will provide all the projects and investigators of the Program Project with a variety of state-of-the-art instrumentation aimed at obtaining measurements in various cells of cell metabolism, ion fluxes, compartmentation of ionic gradients and metabolites, intracellular messengers, etc. as described in the individual sections of the proposal. The instrumentation available through Core C is comprised of several spectrophotometers, fluorometers, HPLC systems, electrometers, amperometric detectors, etc. Part of the instrumentation has been produced commercially and part has been built inhouse and is continually upgraded to fulfill specific research needs. the staff of the core, who has proven expertise in the measurements proposed and in developing state-of-the-art technology, will provide assistance and counseling in the measurements described in the individual projects of this application. The measurements that Core C will carry out include: a) measurements of free intracellular H+ and Ca2+ in cell suspensions, cell monolayers and individual cells; b) kinetic measurement of ion transport across cell and cell membranes; c) microfluorimetric assays of P450 and other enzymatic reaction in small volumes or few cells; d) imaging of cell fluorescence (single cells or several cells) for H+or Ca2+ free intracellular distribution, fluorescent antibody distribution, etc.; e) ion selective electrodes, atomic absorbance, cell permeabilization, etc.; and f) measurements of cell metabolism; ATP/ADP ratios; HPLC of phosphomeabolites, phosphoinositides, etc.